Hitherto, in general, coated tools in which the surfaces of tool bodies made of tungsten carbide (hereinafter, referred to as WC)-based cemented carbide, titanium carbonitride (hereinafter, referred to as TiCN)-based cermet, or a cubic boron nitride (hereinafter, referred to as cBN)-based ultrahigh-pressure sintered body (hereinafter, collectively referred to as a tool body) are coated with a Ti—Al-based complex nitride layer as a hard coating layer through a physical vapor deposition method are known, and it is known that these coated tools exhibit excellent wear resistance.
However, although the coated tool coated with the Ti—Al-based complex nitride layer in the related art has relatively excellent wear resistance, in a case of using the coated tool under high-speed intermittent cutting conditions, abnormal wear such as chipping easily occurs. Therefore, various suggestions for an improvement in the hard coating layer have been made.
For example, JP-A-2009-56540 discloses that a hard coating layer exhibits excellent fracture resistance even under high-speed intermittent cutting conditions, by depositing a hard coating layer which is formed of a layer of a complex nitride of Al and Ti satisfying a composition formula (AlxTi1-x)N (here, x is 0.40 to 0.65 in terms of atomic ratio) and showing a crystal alignment, in which, in a case where crystal orientation analysis is performed regarding the complex nitride layer by EBSD, an area proportion of crystal grains having crystal orientation <100> in a range of 0 to 15 degrees from a normal direction of a surface of a polished surface is 50% or higher, and in a case where an angle between adjacent crystal grains is measured, a proportion of a low angle grain boundary (0<θ≤15°) is 50% or higher, on a surface of a tool body.
However, in this coated tool, since the hard coating layer is deposited through the physical vapor deposition method, it is difficult to set the amount x of Al to be 0.65 or higher. Therefore, it is desired that cutting performance is further improved.
From such a viewpoint, a technology of forming a hard coating layer by a chemical vapor deposition method to increase the amount x of Al to approximately 0.9 has also been proposed.
For example, JP-T-2011-516722 describes that by performing chemical vapor deposition in a mixed reaction gas of TiCl4, AlCl3, and NH3 in a temperature range of 650° C. to 900° C., a (Ti1-xAlx)N layer in which the value of the amount x of Al is 0.65 to 0.95 can be deposited. However, this literature is aimed at further coating the (Ti1-xAlx)N layer with an Al2O3 layer and thus improving a heat insulation effect. Therefore, the effects of the formation of the (Ti1-xAlx)N layer in which the value of the amount x of Al is increased to 0.65 to 0.95 on cutting performance are not clear.
In addition, for example, JP-T-2011-513594 suggests that the heat resistance and fatigue strength of a coated tool are improved by coating a TiCN layer and an Al2O3 layer as inner layers with a (Ti1-xAlx)N layer (x is 0.65 to 0.90 in terms of atomic ratio) having a cubic structure or a cubic structure including a hexagonal structure as an outer layer, and applying a compressive stress of 100 to 1100 MPa to the outer layer.